This invention relates generally to cannulas adapted for both mouth and nasal use to both monitor breathing and deliver a gas, in particular, a method of manufacturing a cannula adapted to interconnect with both nasal passages and the mouth for use to monitor breathing, especially for the detection of apnea.
Nasal cannulas are commonly used to administer gases, such as oxygen, to humans having respiratory problems. Illustrations of nasal cannulas used for this purpose are found in U.S. Pat. No. 3,802,431. Nasal cannulas have been used also for inhalation therapy, made possible by development of inhalation sensors such as described in U.S. Pat. No. 4,745,925. A nasal cannula can be used to monitor breathing and for detection of apnea (the absence of breathing) when connected to an inhalation sensor.
Nasal cannulas additionally adapted to communicate with the mouth of humans to permit administration of fluids or sensing of apnea during periods of mouth breathing or nasal blockage are also known.
The present invention is a novel cannula and method of manufacturing a cannula to communicate with both nasal and oral passages. This method provides in the preferred embodiment, disconnectable mandrels, which when assembled form a mold over which a cannula forming polymeric material is applied, and which, through the capability of being disconnected, each mandrel part from the other(s), facilitates removal of the mandrels from the formed cannula.
The prior art of dipping a part in a plastisol to create a coating thereof is exemplified by U.S. Pat. Nos. 3,906,071, 4,695,241 and 4,800,116, the disclosures of which are hereby incorporated by reference.